1. Field of the Invention
The present invention relates to power saving for a mobile device in a wireless communication system, and more particularly, to a power saving method, which switches the mobile device to different connection states according to a screen status of the mobile device and related mobile device.
2. Description of the Prior Art
The third generation (3G) mobile communications system has adopted a Wideband Code Division Multiple Access (WCDMA) wireless air interface access method for a cellular network. WCDMA can provide high frequency spectrum utilization, universal coverage, and high quality, high speed multimedia data transmission. The WCDMA method also meets all kinds of QoS (Quality of Service) requirements simultaneously, providing diverse flexible two-way transmission services and better communication quality to reduce transmission interruption rates.
In the WCDMA protocol, a fast dormancy feature can allow wireless communication device go to idle directly (shown in FIG.1) or go to Cell_PCH state (or Cell_FACH state) in certain period (shown in FIG. 2). While no data transmission and reception, a mobile device can send different types of SCRI (Signaling Connection Release Indication) to trigger the network to indicate the mobile device to go to Cell_PCH (or Cell_FACH) or idle state.
The Cell_PCH (or Cell_FACH) state can allow the mobile device re-setup the wireless link faster than the idle state. However, generally, the Cell_PCH (or Cell_FACH) state has smaller DRX cycle length than the idle state, as shown in FIG. 3 and FIG 4. The smaller DRX cycle length, however, costs more average standby current.
Because a mobile device may be powered by a battery, use of these features causes the battery level to reduce. The battery must eventually be recharged, which maybe inconvenient to a user. Thus, a desire exists for reducing power consumption in mobile devices in order to prolong time between battery charges.